Western North America Mercury Synthesis (WNAMS)

Transcription

1 Western North America Mercury Synthesis (WNAMS) A Multi-disciplinary, tri-national assessment of the climate, landscape, and land use controls on mercury risk to ecological and human health across western North America US Geological Survey Biodiversity Research Institute University of Wisconsin, La Crosse Harvard University

2 Global Continental UNEP Global Binding Mercury Treaty United States - MercNet Regional North America - CEC Northeast Great Lakes Western Southeast

3 The Database: MercNet Primary Purpose A one-stop spot for access to a comprehensive Hg dataset Identification of geographic and temporal patterns Geographic scope United States Timeframe All years of available data Data sources Federal and state agencies Peer-reviewed literature >500,000 Hg data points Data types Air, water, sediment/soils, vegetation, invertebrates, fish, birds, and mammals

4 Past Regional Synthesis Efforts -Northeast US and Canada- Mercury Database includes: Air, Water, Sediment Cores Sediment Lower Food Web Fish Birds Mammals >60,000 data points

5 Northeast Regional Synthesis: Study Area: New York, New England, Quebec, and Canadian Maritimes 3 workshops participants / workshop Journal: Ecotoxicology (2005 Vol. 14; 21 papers) Bioscience 2 papers BRI Communications Piece: Mercury Connections

6 Past Regional Synthesis Efforts -Great Lakes- Mercury Database includes: Air, Water, Sediment Cores Sediment Lower Food Web Fish Birds Mammals >300,000 data points

7 Great Lakes Regional Synthesis: Study Area: Great Lakes states (8 of them) and Ontario Journal: Ecotoxicology (2011 Vol. 20; 22 papers) and Environmental Pollution (2012 Vol. 161; 13 papers) 35 total papers BRI Communications Piece: Mercury Connections

8 Tri-National Collaboration Western North America Hg Synthesis

9 Tri-National Collaboration Initial support from USGS Powell Center and the National Park Service

10 Western Regional Synthesis: Goals 1. Synthesis of existing Hg and ancillary data in Western N. America: a) Evaluate factors that control Hg cycling and bioaccumulation: major source, land use, transport, and climate b) Identify risk to key biological resources c) Link Hg transport and chemistry with ecological exposure. 2. Engage the entire community of Hg scientists, resource managers and stakeholders (Governmental and NGO) 3. Provide foundational science to help guide regional scale management with respect to Hg risk to human and ecosystem health

11 Western Regional Synthesis: Key Questions 1. Spatial patterns a) Across matrices b) Importance of source type c) Latitudinal changes 2. Temporal patterns a) Across matrices b) In relation to changes in land use/cover, climate, emissions 3. Landscape effects a) Relative importance of source vs. habitat type b) Linkage between methylation and bioaccumulation across habitats

12 Western Regional Synthesis: 4) Habitat types a) Which pose greatest Hg risk to wildlife and ecosystem health? b) What defines Hg-sensitive landscapes? 5) Climate Change Key Questions (cont.) What changes in Hg transport and bioaccumulation can be predicted based on expected climate change models? 6) What are the implications for the management of public lands; and what knobs exist? 7) What are the policy implications (nationally, regionally and globally)?

13 Western North America Hg Synthesis Study Area: Western United States, Canadian-Alaska Arctic, Mexico Journal: Science of the Total Environment (2016, 15+ papers)

14 Science of the Total Environment Issue 1) A synthesis of terrestrial mercury in the western United States: Spatial distribution defined by land cover and plant productivity 2) Avian mercury exposure and toxicological risk across western North America: A synthesis 3) **Comparison of mercury mass loading in streams to atmospheric deposition in watersheds of Western North America: Evidence for non-atmospheric mercury sources 4) Estimating mercury emissions resulting from wildfire in forests of the Western United States 5) Hg concentrations in fish from coastal waters of California and Western North America

15 Science of the Total Environment Issue 6) Hydrologic indicators of hot spots and hot moments of mercury methylation potential along river corridors 7) Mercury and methylmercury in aquatic sediment across western North America 8) Mercury risk to avian piscivores across Western United States and Canada 9) Reservoirs and water management influence fish mercury concentrations in the western United States and Canada 10) Spatial and temporal patterns of mercury concentrations in freshwater fish across the Western United States and Canada

16 Science of the Total Environment Issue 11) Trends in mercury wet deposition and mercury air concentrations across the U.S. and Canada 12) Spatiotemporal patterns of mercury accumulation in lake sediments of western North America 13) Surface-air mercury fluxes across Western North America: A synthesis of spatial trends and controlling variables

17 Comparison of Mercury Mass Loading in Streams to Atmospheric Deposition in Watersheds of Western North America: Evidence for non-atmospheric Mercury Sources Joseph Domagalski, Michael S. Majewski, Charles N. Alpers, Chris S. Eckley, Collin A. Eagles-Smith, Liam Schenk, Susan Wherry

18 Compared annual riverine loads of total Hg (THg) at selected river locations to annual estimates of wet and dry deposition over the upstream watersheds. Investigated 27 watersheds 15 with some degree of mining (Hg, Au, Ag) 10 in pristine or areas of low development 2 mostly urban Watershed size: Small <1 km² to large 69,455 km² Arctic 852,257 km² and 1,289,036 km²

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20 Land use: Ranges from largely pristine to having variable levels of anthropogenic disturbance including urbanization, agriculture, and mining. Climatic conditions: Variable, especially with respect to rainfall. Quantify the relative importance of atmospheric and nonatmospheric Hg sources/pathways to stream loads. Wet & Dry deposition typically more than streamflow transports out. Estimate the amount of Hg stored in each watershed. Study years:

21 Data Sources: Wet Deposition Mercury Deposition Network (MDN, >100 sites, but most are east of the Rocky Mountain States.

22 Data Sources: Dry Deposition No National sampling network and few direct measurements have been made. Community Multi-scale Air-quality (CMAQ) model Much coarser grid (40 km x 40 km vs. 800 m x 800 m) Only 2009 monthly data available Does not account for year-to-year variability. A recognized limitation.

23 Data Sources: Arctic Wet and Dry Deposition Global/Regional Atmos. Heavy Metals Model (GRAHM, Dastoor and Davignon, 2009)

24 Data Sources:

25 Data Sources: Stream Loads: Data obtained from published literature or Calculated from concentration and stream flow data (NWIS) Annual THg loads calculated using regression of concentration against discharge, time, seasonality: LOADEST (Cohn et al., 1989; Crawford, 1996; Runkel et al., 2004) Requires at least 1 year of data with a minimum of 20 samples collected over the year EGRET (Hirsch and DeCirro, 2014) Requires at least 20 years of data

26 Data Sources: Climate Divisions:

27 Data Sources: Palmer Drought Severity Index (PDSI)

28 Results: The THG ratio of annual stream load to deposition varied considerably across the study areas and 13-year time frame A ratio of 1 indicates THg sources other than atmospheric deposition

29 Results: Diagonal lines indicate constant stream load (yield) to atmos. dep. ratio values. A) Effect of watershed type and size on stream load. B) Area normalized atmos. Hg dep. and watershed THg yield.

30 Summary: Watersheds have geologic, anthropogenic, and global atmospheric Hg sources The ratio of THg exported by streams relative to atmospheric deposition is highly variable. Abandoned mines increased annual stream load relative to deposition. THg loads in small watersheds with Hg, Au, or Ag mining are higher relative to atmospheric deposition. Watershed area is important Lower ratios in large watersheds with mining indicate: Soil absorption of Hg Less precipitation mobilizing Hg Trapping of sediments by reservoir dams

31 Summary: Watersheds in urban area had > Hg loads/unit area than vegetated areas impervious areas Watersheds with forested and other natural vegetation have attenuated river loads. The Arctic watersheds had elevated ratios likely caused by the mobilization of Hg from the thawing permafrost due to climate change. Smaller watersheds are more predictable with respect to contaminant sources. The signals get lost/mixed as the watershed size increases.